Fernando Luiz B. Ribeiro

Streaming SIMD Extensions applied to boundary element codes

Nowadays processor architectures include Streaming SIMD Extensions (SSE) originally developed for multimedia applications, not so well explored for scientific computing. This fact has called the attention of the present authors and this paper introduces the application of SSE, also known as multimedia instructions, to boundary element codes. Since SSE instructions are not widespread among boundary element programmers, the authors present this technique applied to a well-known Fortran program for the solution of two-dimensional elastostatic problems. The vectorization guidelines provided here may also be extended to other numerical methods. Numerical experiments show the effectiveness of the proposed approach.

Determining the adiabatic temperature rise of concrete by inverse analysis: case study of a spillway gate pier

This paper presents a method to find the adiabatic temperature rise of concrete by retro-analysing temperatures measured in the field. The construction phase is simulated with a 3D finite-element model that considers the coupling between thermal and chemical phenomena due to cement hydration. A genetic algorithm is used to find the main parameters that characterise the adiabatic temperature curve and that better fit the temperatures measured in the field for a given structure. This method was applied to the construction of the spillway gate pier of a hydroelectric power plant. The good agreement between numerical results and temperature measurements points to the feasibility of the proposed method.

A thermoregulation model for hypothermic treatment of neonates

This paper presents a thermoregulation finite element model (FEM) to simulate hypothermia procedures for the treatment of encephalopathy hypoxic-ischemia (EHI) in neonates, a dangerous ischemic condition that can cause neurological damages and even death. Therapeutic hypothermia is the only recommended technique to reduce sequels caused by EHI in neonates; intervention with moderate cooling for neural rescue in newborns with hypoxic-ischemic brain injury is the culmination of a series of clinical research studies spanning decades. However, the direct monitoring of brain cooling is difficult and can lead to additional tissue damage. Therefore, the measurement of efficiency during clinical trials of hypothermia treatment is still challenging. The use of computational methods can aid clinicians to observe the continuous temperature of tissues and organs during cooling procedures without the need for invasive techniques, and can thus be a valuable tool to assist clinical trials simulating different cooling options that can be used for treatment. The use of low cost methods such as cooling blankets can open the possibility of using brain cooling techniques in hospitals and clinics that cannot currently afford the available expensive equipment and techniques. In this work, we developed a FEM package using isoparametric linear three-dimensional elements which is applied to the solution of the continuum bioheat Pennes equation. Blood temperature changes were considered using a blood pool approach. The results of the FEM model were compared to those obtained through the implementation of a user-defined function (UDF) in the commercial finite volume software FLUENT and validated with experimental tests. Numerical analyses were performed using a three-dimensional mesh based on a complex geometry obtained from MRI scan medical images.

A thermoregulation model for whole body cooling hypothermia

This paper presents a thermoregulation model based on the finite element method to perform numerical analyses of brain cooling procedures as a contribution to the investigation on the use of therapeutic hypothermia after ischemia in adults. The use of computational methods can aid clinicians to observe body temperature using different cooling methods without the need of invasive techniques, and can thus be a valuable tool to assist clinical trials simulating different cooling options that can be used for treatment. In this work, we developed a finite element method (FEM) package using isoparametric linear three-dimensional elements which is applied to the solution of the continuum bioheat Pennes equation. Blood temperature changes were considered using a blood pool approach and a lumped analysis for intravascular catheter methods of blood cooling. Some analyses are performed using a three-dimensional mesh based on a complex geometry obtained from computed tomography medical images, considering a cooling blanket and an intravascular catheter. A comparison is made between the results obtained with the two techniques and the effects of each case in brain temperature reduction in a required period of time, maintenance of body temperature at moderate hypothermia levels and gradual rewarming.